Defective Or Used Honda City Car Instead Of A New One

I  bought a new Honda city recently in Ranchi. The car looked perfect, but it was a defective one. When we bought the car, and after payment procedures, the owner of the showroom abruptly said in a cunning voice that now the car is yours, and we will now not be responsible for any damage as we have checked the car well. We didn't understand why did he replied in such a clumsy voice, but one day when we went for the servicing of car about one month of the purchase at Honda service station and the worker said that it had lots of bumps under the car which became visible when the car was lifted up for washing. Also the engine oil tank was seriously damaged and a lot of patch work was done to stop the oil from coming out. We went to the dealer to talk to him but he replied very badly, not listening a word and repeating the same thing when we had bought the car. They said that we have made the bumps and damaged the engine oil tank. But I knew that this is not the truth. We want justice and want this car to be replaced with a new one as no one would like to drive a damaged or repaired old car. We are sure that the car was damaged since the time we purchased it and this should be the responsibility of the dealer to replace it. I want the conerned authorities not to take it lightly and take appropriate steps.